A horny layer that forms the outermost layer of the skin has the functions of inhibiting penetration of substances from the outside and volatilization of moisture from the inside of the skin and of maintaining a flexibility and a smooth appearance of the skin by virtue of moisture held by the horny layer itself. The horny layer is constituted from horny cells, and a lipid called a horny intercellular lipid (hereinafter referred to as a horny ICL) forms a stratified structure between the spaces of the horny cells to fill up the spaces between the horny cells.
A ceramide accounting for about 50% of this horny ICL attracts attentions as an active ingredient for the skin reduced in moisture such as rough skin, dry skin or aged skin. Further, it is also known that the state of a horny layer reduced in a performance can be improved by externally supplementing a ceramide as a component for improving a horny layer performance (J. Invest. Dermatol., 84: 282 (1985) and J. Invest. Dermatol., 87: 758 (1986).
However, ceramides, including natural ceramides, are substances having a very high melting point and a strong crystallinity. Accordingly, a large amount of an oil and a surfactant has to be used in order to prepare a stable skin external preparation. As a result thereof, the properties of a skin external composition containing ceramides have been restricted, and therefore the use feeling has inevitably been further reduced.